Question: Kevin is 4 times as old as Vanessa and is also 15 years older than Vanessa. How old is Vanessa?
Answer: We can use the given information to write down two equations that describe the ages of Kevin and Vanessa. Let Kevin's current age be $k$ and Vanessa's current age be $v$ $k = 4v$ $k = v + 15$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $v$ , and both of our equations have $k$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $4v$ $-$ $ (v + 15)$ which combines the information about $v$ from both of our original equations. Solving for $v$ , we get: $3 v = 15$ $v = 5$.